Bladed rotor



April 9, 1946- F. A. M. 'HEPPNER 2,398,140

BLADED ROTOR Filed Aug. 11, 1944 INVENTO/F .524 Ina-. 6

Patented Apr. 9, 1946 BLADED ROTOR Fritz Albert Max Heppner, LeamingtonSpa, England, assignor to Armstrong Siddeley Motors Limited, Coventry,England Application August 11, 1944, Serial No. 549,037

In Great Britain December 8, 1943 6 Claims.

This invention relates to a rotor having a pcripheral row of blades.

One of my objects is to provide a blade lock. and particularly one whichcan be used in the casein which the blades carry relatively-thin fiatshrouds at their outer ends which form a ring when the parts areassembled, as the existence of any lock eliminates or at least reducesbending stresses at the blade root.

In the accompanying sheet of drawings:

Figure 1 is a fragmentary, part-sectional; elevational view of acompound rotor according to the invention, the view showing twocompressor blades with shrouds carrying externally turbine blades andthe view of the rotor being a section taken on the line II of Figure 2;

Figure 2 is a cross-section through a part of the rotor with acompressor and turbine blade shown in elevation, the view being from theright of Figure 1;

Figure 3 is a fragmentary plan view of two shrouds whencircumferentially separated from one another; and

Figure 4 is a fragmentary perspective view of the slotted end of ashroud.

According to one feature of the invention, the blades carryrelatively-thin shrouds at their outer ends which form a ring when theparts are assembled, and each adjacent pair of shrouds is interlockedagainst lateral or radial movement by means of oppositely-inclined slotsin the mating edge of one shroud of a pair and acomplementary pair ofprojections on the mating edge of the other shroud, whereby the shroudscan move in a circumferential direction during assembly or dismantlingof the parts.

Preferably, there are only two slots in each of the appropriate matingedges, one slot being narrower than and imposed upon the other. Theslots may be at right-angles to one another, for example, inclined tothe fiat surfaces of a shroud at approximately 45".

In the construction shown in the drawings, the rotor l2 has a deepperipheral groove l3 in it and the walls thereof-are parallel to oneanother and formed with toothed spiral ridges I4 in the manner disclosedin the specification accompanying my patent application No. 484,915,filed April 28,

1943. Each compressor blade I5, the form of which is indicated by thechain lines I6, is formed with a root l1 opposite faces of which aretoothed to enable it to be secured by a screwing action in theperipheral groove l3. The other two opposite faces of the blade root aregrooved as shown at l8 for lightening purposes, but there remainsbetween the two grooves l 8 a body of metal through which passes aradial line 20 on which the centres of gravity of various cross-sectionsof the blade approximately lie. Incidentally, the centres of gravity ofvarious cross-sections of the associated turbine blade 2| alsoapproximately lie on this same radial line.

The compressor blade carries at its outer end a flat shroud 23 which inturn supports the turbine blade (the form of which is indicated by thechain line 24) and it is desirable, as stated, to interlock the abuttingedges of each pair of shrouds as the existence of any such lock reducesbending stresses at the blade root to a great extent. Both ends of acompressor blade being in effect held, the result is that bending of acompressor blade is negligible. Actually, bending in a turbine bladetakes place in approximately only half its length, and vibrations areonly possible on the short length of the turbine blade where bending canoccur.

As will be seen particularly from an examination of Figures 3 and 4, theinterlock consists of 25 two transverse grooves 25, 26 of which theformer is narrower than and imposed upon the latter, whilst the matingedge of the other shroud is formed with complementary projectionsindicated at 21. Such a form of interlock will allow the shrouds toapproach one another in a circumferential direction-as is necessary whenthe individual compressor blades are being screwed into the rotor, yetwhen the parts are assembled it is impossible for the shrouds to moveradially or laterally with respect to one another.

The particular form of interlock disclosed'can be easily manufactured,and it can be satisfactorily applied to thin shrouds. The lock itself isso sturdy that the shroudswork under safe stresses.

Withthe construction shown it is possible to form a compound rotor foran internal-combustion turbine plantin which some or all of the shroudscarry externally blades forming an outer row, such shrouds beingintegrally united to their associated supporting blades.

What I claim as my invention and desire to secure by Letters Patent ofthe United States is 2 1. A rotor having a peripheral row of blades, thelatter carrying relatively-thin, flat shrouds at their outer ends, theshrouds forming a ring when the parts are assembled, each adjacent pairof shrouds being interlocked against lateral and radial movement bymeans of oppositely-inclined grooves in the mating edge of one shroud ofa pair dismantling of the parts.

2. A rotor, according to claim 1, in which there are only two grooves ineach of the appropriatemating edges, one groove being narrower than andimposed upon the other groove.

3. A rotor, according to claim 1, in which there are only two grooves ineach of the appropriate mating edges, one groove being narrower than andimposed upon the other groove, and the grooves being inclined to theflat surfaces of a shroud at approximately 45.

4. A rotor having a peripheral row of blades, the latter carryingrelatively-thin, flat shrouds at their outer ends, the shrouds forming aring and having means at their edges by which they are adapted tointerlock with one another (against radial and lateral movement) whenthe parts are assembled, theinterlocking means being such as to allow orrelative circumferential movement between the shrouds, the blade rootsbeing formed. with teeth, and the rotor being formed with complementaryspiral ridges in opposite sides of a parallel-sided peripheral groove inthe rotor to engage said teeth such that the blades, whilst beingscrewed in during assembly, will move radially inwardly until theirroots abut one another and their shrouds interlock.

5. A rotor, according to claim 4, in which the blade roots are formedwith flanges adapted to overlap and engage the side faces of the rotor.

6. A rotor, according to claim 4, in which some at least of the shroudscarry externally blades forming an outer row, such shrouds being in-'tegrally united to their associated blades.

FRITZ ALBERT MAX HEPPNER.

